1. Field of the Invention
The present invention relates to a load port device for conveying a container including a gas port and an internal space from a processing apparatus, and also relates to a transport system and a container carrying out method in which this load port device is used.
2. Description of the Related Art
A load port device is, for example, a device that moves sealed containers containing substrates in and out of an automated warehouse or a semiconductor processing device. The sealed containers are conveyed by a transportation vehicle from the load port device to another device (see Japanese Laid-Open Patent Application 2010-64806, for example).
The sealed container is a FOUP or a SMIF, for example. When a circuit board is to be conveyed or stored, the container is put in a sealed state, which prevents dust from finding its way inside the container.
Also, the growth of an oxide film caused by natural oxidation of a semiconductor substrate is prevented by replacing the internal atmosphere of the sealed container with nitrogen gas or another such inert gas.
The nitrogen gas concentration inside the sealed container sometimes drops below the specified level during storage or while waiting for conveyance. When this happens, the sealed container whose concentration of nitrogen gas has decreased is repurged. The operation for purging a sealed container will now be described below. A gas supply port and an exhaust port that communicate between the inside and outside are formed in a conveyable sealed container. A gas supply apparatus includes a gas supply nozzle connected air-tightly to the gas supply port, and an exhaust nozzle connected air-tightly to the exhaust port. The gas supply nozzle is connected via a gas supply pipe to a gas supply source that supplies purge gas. The gas exhaust nozzle is connected to a processing apparatus that performs exhaust. The purge gas is supplied from the gas supply source, through the gas supply pipe, the gas supply nozzle, and the gas supply port, into the conveyable sealed container. When the sealed container is filled with the purge gas and the inside of the sealed container exceeds a specific pressure, the purge gas is exhausted through the exhaust port, the exhaust nozzle, and an exhaust pipe.
With a load port device provided to a stocker, the sealed container is conveyed by a conveyor from inside the stocker to a standby position. The sealed container stays at the standby position until loaded onto a transportation vehicle. However, nitrogen gas concentration in the sealed container will also continue to decline during the time it takes for the transportation vehicle to arrive.